The electronic configuration, of an element of atomic number 7, is $1s^{2}\,2s^{2}\,2p^{2}_{x},\,2p^{1}_{y}\,2p^{1}_{z}$. Thus the valency shell is second principal shell which has only four orbitals. Therefore the element can form maximum of four covalent bonds. Thus the covalency is 4.